Patient demand for more esthetic dental restorations has led to a renewed interest in all-ceramic crowns. however, despite the introduction to the dentist of several innovative commercial systems, crown fracture remains a clinical problem. There are gaps in our present knowledge of how these clinical failures occur, the durability of the available systems, and the effect of the environment around the restoration. Most reported studies have ignored the effects of stress-corrosion of glass and ceramics has been studied in relation to many industrial applications, such as optical fibers, and several promising advances have been made in, for example, coating techniques. These procedures have yet to be tested in dental applications. The proposed research aims to increase the scientific knowledge governing fracture mechanics of dental ceramics and identify ways that fracture resistance of currently available materials can be increased. This will be accomplished in four phases; 1) A sample of failed restorations from clinical practice will be studied by fractography to determine the site of fracture initiation and stress levels involved. 2). Room temperature strength and color measurements of dental ceramics will be made for a range of surface treatments and environments. Treatments will include three different luting agents, five types of surface coatings selected from the ceramic engineering literature, different etching regimens to reduce flaw size, and ion-exchange strengthening. 3). Further testing will be done on those treatments found to be the most effective. A dynamic fatigue method will be used to determine influence on stress- corrosion susceptibility. 4). the methods found to reduce susceptibility will be applied to the fabrication of simulated dental crowns which will be tested with a liquid nitrogen method. Results will be used to predict time to failure of the improved dental restorations.